Resistor



June 10, 1941. G. L, PEARSON 2,421,759

RESISTOR Filed Jan. 5, 1944 FIG. I

E 1 A I/ INVENTUR G. L. PEARSON flimaudirdunb A from/Er Patented June 10, 1947 RESISTOR Gerald L. Pearson, Chatham, N. J.,- assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application January 5, 1944, Serial No. 517,061

2 Claims.

This invention relates to resistors and more particularly to resistors of very small volume and iaving a temperature coefiicient of resistance of relatively high absolute value.

Resistors, the resistance of which varies greatly with changes in temperature, have for convenience of terminology been called thermistors. Wherever the term thermistor is used in this specification or the appended claims, such a resistor i intended.

It has been found that for many applications thermistors in order to properly perform their functions must be very small in size. Small thermistors have usually been made in the form of a tiny bead of suitable resistance material having conductive leads embedded therein; or of small cylinders or pellets of like material with conductive leads secured to opposite ends thereof. Diiiiculties have been encountered in making bead or pellet type thermistors of sufficiently small volume to meet certain electrical and thermal requirements.

In the light of the foregoing, an object of this invention is a very small resistor with a relatively high absolute value of resistance-temperature coefficient and having a high resistance and high sensitivity.

A feature. of this invention resides in a very fine filament of tough, flexible, insulating material, which provides a base for the current carrying portion of the improved resistor.

A further feature of this invention involves a layer of high resistance-temperature coefficient, resistance material adhering to an intermediate portion of the filament of insulating material.

Another feature of the invention resides in thin films of metallic conductive material coating the remainder of the insulating filament and making contact respectively to spaced portions of the high resistance-temperature coefficient material.

Other and further objects and features of this invention will appear more fully and clearly from the following description of an illlustrative embodiment thereof taken in connection with the appended drawings in which:

Fig. 1 is a sectional view at an enlarged scale of a portionof a resistor illustrating the invention; and

Fig. 2 is a view at an enlarged scale partly in section showing a resistor, made in accordance a filament II of insulating material having a band I2 of resistance material adhering to an intermediate portion thereof. The remainder of the filament II is coated with continuous layers I3 and I4 of conducting material, which make contact respectively with opposite ends of the band I2.

The band I2 may be made of any suitable resistance material. For example, uranium oxide hasbeen used to make the resistance band. One way of doing this is to apply a paste of uranium oxide powder and water or uranium nitrate to an intermediate portionof the filament It. The paste may then be subjected to a sufficiently high temperature to sinter the oxide material and cause it to adhere firmly to the filament. After the sintered material has cooled metallic films I3 and I4 may be applied to the filament,- making sure that they are in good contact with the band of resistance material I2. This may be done by masking or otherwise protecting all of the band I2 except its ends and then vapor depositing a metallic film on the filament and the ends of the resistor H. A suitable material for the adherent films I3 and I4 is gold.

The filament II may be made of any insulating material that can be successfully reduced to a very small cross section. A particularly suitable material for the filament is quartz, which may be drawn out very fine and stilPretain considerable strength.

For protection the thermistor I0 may be enclosed in an envelope as illustrated in Fig. 2. The envelope may be a tube or bulb I5 of glass or like suitable material. The thermistor assembly It may be secured to mounting or supporting conductors I6 and I! which may be sealed into the ends of the tube I5. One Way of securing the thermistor assembly to the supporting conductors is to slightly flatten each conductor I6 and I1 and to secure the ends of the metal coated filament II to each fiat portion by means of a suitable conducting cement. The cement may be colloidal graphite in water, the water being evaporated to solidify the cement. If desired, the tube I5 may be evacuated and then sealed off as at I8.

The filament II, if made of quartz, may be of the order of a few mils to a fraction of a mil in diameter and the band I2 of a thickness comparable to the diameter of the filament. Due to the particular structure and the very small dimensions, it is obvious that a very minute volume and cross section of resistance material may be made. Thus the desired high resistance and high sensitivity to applied power is obtained.

Although this-invention has been disclosed by means of an illustrative embodiment thereof, it will be understood that it is not limited thereby but by the scope of the appended claims only.

What is claimed is:

l. A high resistance-temperature coeiilcient resistor having high sensitivity to applied power and comprising a fine filament of quartz havin a diameter of the order of a few mils to a fractlon of a mil, a layer of high resistance-temperature coefiicient resistance material of a thickness comparable to the diameter of said filament ad hering to an intermediate portion of said filatnent and forming a continuous band therearound, and films of metallic, conductive material coating the remainder oi. the filament, said films maldng contact respectively with opposite edges of the band of resistance material.

2. A high resistance-temperature coefiicient resistor having high sensitivity to applied power the remainder of the filament, said films making contact respectively with opposite edges of the band of uranium oxide.

GERALD L. PEARSON.

REFERENCES CITED The following references are 01' record in the file of this patent:

UNITED STATES PATENTS Name Date Dubilier Dec, 4, 1928 Pende'r July 22, 1930 Pender Nov. 1'7, 1931 Weintraub May 9, 1922 Number 

